Platelet factor XIII is an active enzyme after solubilization and crossed immunoelectrophoresis

Crossed immunoelectrophoresis of platelets against antiplatelet antibodies has proved to be a valuable tool in the study of platelet proteins (1-8). The advantage of this separation system is that the proteins are separated under nondenaturating conditions and thus to some extent would be expected to maintain their functional properties. Previously, the binding of several proteins to immobilized thrombin (5) and immobilized heparin (9) during crossed immunoelectrophoresis of platelet proteins solubilized in a Triton X-loo-containing buffer has been described. Furthermore, it has been demonstrated that fibrinogen is able to bind to immunoprecipitates containing the glycoprotein IIb-IIIa-complex (7). These studies indicate that the proteins contained in the immunoprecipitates represent biologically active entities. In the present study we provide direct evidence for this by demonstrating enzymatic activity associated with the immunoprecipitate containing Factor XIII in immunoplates obtained after crossed immunoelectrophoresis of solubilized platelets against anti-platelet antibodies.